In air-conditioning, refrigeration, heat-pumping, and other refrigerant-based systems, heat is removed from a colder side of a device or system and transferred to a warmer side. For example in the case of air-conditioning, heat is transferred from the interior of a building, vehicle or other enclosed space to the exterior atmosphere. A standard process of removing colder air from one chamber and transferring it to another chamber or area includes four steps: compression of a refrigerant, followed by heat expulsion to the warm side, followed by a sudden expansion or other means of decompression, and finally absorption of heat from the cold side.
According to a typical prior art system, such as that illustrated in FIG. 1, both a compressor and a heat exchanger are separately required to accomplish the first two steps of the refrigeration cycle. As illustrated, the prior art air-conditioning/cooling system 100 defined by a refrigerant loop includes a compressor 110 that compresses the refrigerant fluid (typically a gas at that stage) by pressurizing it, which causes its temperature to increase in the output, compressed refrigerant. An electrical (or other power source) drive typically delivers the mechanical energy required to perform the compression of the refrigerant. The compressor typically uses an impeller or piston or other arrangement to compress the refrigerant. As shown, the refrigerant flows through the system loop 100 in accordance with the flow arrows 121.
The system 100 also includes a condenser 120, comprising an exterior coil 122, that provides a surface area capable of sufficient heat exchange as the heat generated by the (heated) pressurized refrigerant within the coil is transferred to the exterior (cooler side) by the atmospheric air (or other transfer fluid) passing over the coil. This causes the refrigerant to expel heat and liquefy. Once a sufficient amount of heat is removed, the refrigerant is expanded and decompressed in an expansion valve 125, causing its temperature to drop to a temperature below that of the cold chamber. The refrigerant subsequently enters a heat exchanger 132, where it flows trough a set of coils 131 and is exposed (typically by means of a fan 140) to the air of the cold chamber, from which, by virtue of the refrigerant's lower temperature, heat is extracted and communicated to the refrigerant, which vaporizes in the process (i.e. the refrigerant “absorbs” the heat).
As the refrigerant passes through the heat exchanger 132 (consisting of coil 131 and fan 140) inside the chamber 130 and becomes warmer, heat is transferred from the surrounding space 132 by a fan 140 (or alternatively ram air, as in the case of vehicle motion), and produces cool air that is ejected into the space being the object of cooling. The refrigerant returns to a vapor phase based upon the heat withdrawn from the air that passed over the coil 131. The refrigerant vapor then returns to the compressor 110 to become a high-pressure gas again. The heat then flows from the high-temperature gas to the lower-temperature air of the space surrounding the coil 122. This heat loss causes the high-pressure gas to condense to liquid, which again passes through expansion valve 125 into coil 131 inside the chamber 130 to repeat the compression, and then condensation cycles. This process is continually performed to condition air in compartments (i.e. cool or heat) as desired.
A disadvantage of the air-conditioning arrangement illustrated in FIG. 1 is that it requires a compressor to first pressurize the refrigerant so that it becomes high-pressure, heated gas, a condenser for providing the heat exchange required to cool down the refrigerant before it passes into the coil within the refrigerant compartment, and an expansion valve. This typically requires three separate and discrete devices, one for performing each process within the air-conditioning/refrigeration cycle and interconnected by appropriate tubing. This reduces efficiency and increases component count and cost. More particularly, it is a well-established fact of thermodynamics that, at identical pressures, more energy is required to compress a gas at a higher temperature than the same gas at a lower temperature. Thus, compression with delay of heat expulsion until completion of the compression requires more energy than compression with anticipated heat expulsion during the compression. The ability to carry out this process in a more-isothermal manner, in which heat is removed from the refrigerant simultaneously with the compression, can provide a more-efficient overall process. Another disadvantage is the physical separation of the expansion valve 125 from the compressor 110, which prevents transfer of energy removed from the fluid during expansion to the compressor in order to reduce its energy demand.
Various systems have attempted to overcome this disadvantage, including providing systems having multi-stage compression components separated by intermediate cooling stages, on one hand, and systems with expansion through a turbine sharing a rotating shaft with the compressor, on the other hand. However, these systems typically require an increased number of components relative to a conventional arrangement, for example a first-stage compressor, flash chamber, heat exchanger, and second-stage compressor. These multi-stage systems have typically been limited to large-scale refrigeration systems due to the number of components (and associated higher cost) required for operation. This cost and complexity renders such systems, undesirable for smaller scale air-conditioning and refrigeration applications.
According to prior art arrangements, piston-type compressors are provided that include cooling jackets that remove heat from the compressor wall to enhance isothermalism, and/or intermediate heat exchangers between the stages of a multi-stage compressor assembly. However, these compressors operate with a reciprocating piston that does not allow sufficient physical proximity between the refrigerant under compression (inside the piston chamber) and the fluid (such as atmospheric air) used for the cooling, and only a fraction of the heat can be extracted during the compression. There is currently no available system in which a large portion of cooling (and condensation) occurs during the compression cycle to improve efficiency, particularly, one which does not involve a series of separate components that increase cost and complexity.
It is thus desirable to provide a single apparatus capable of performing simultaneous refrigerant compression, condensation, and expansion, thereby improving efficiency and overall design of air-conditioning, refrigeration and heat-pumping systems. This system should further provide the advantage of a fewer number of components for performing the required heat transfer from a cold side to a warmer side.